Rice Mutant, d14, Shows Enhanced Tillering due to Insensitivity to Strigolactones

Abstract

The growth and development of plants are heavily influenced by the pattern of shoot branching. Axillary buds, which are formed in the axil of leaves, play a key role in shoot branching. The outgrowth of axillary buds is regulated by a complex interaction of environmental and endogenous cues. Recent studies have identified a group of highly branched mutants in different plant species, including Arabidopsis and pea, which have provided insights into the molecular mechanisms controlling shoot branching. These mutants are deficient in either the synthesis or signaling of a graft-transmissible branch-inhibiting hormone. One of these mutants, d14, in rice, has shown reduced sensitivity to strigolactones, a class of plant hormones known to inhibit shoot branching. In this article, we discuss the role of the d14 gene in the strigolactone pathway and its implications for the regulation of shoot branching in rice.

Introduction

The branching pattern of plants is crucial for their overall architecture. Shoot branching starts with the formation of axillary buds in the leaf axils. These buds can remain dormant or grow, depending on various environmental and internal factors. The control of axillary bud outgrowth is complex and involves the interplay of multiple genetic pathways. In recent years, significant progress has been made in unraveling the molecular mechanisms underlying shoot branching in different plant species, including pea, Arabidopsis, and rice. These studies have identified several mutants that are impaired in the synthesis or signaling of a branch-inhibiting hormone. Among these mutants, the d14 mutant in rice has been found to be insensitive to strigolactones, a class of plant hormones that inhibit shoot branching. In this article, we investigate the role of the d14 gene in the strigolactone pathway and its impact on shoot branching in rice.

Results

The d14 mutant in rice displays a dwarf phenotype and increased tiller numbers, similar to other mutants in the strigolactone pathway. To confirm that d14 functions in the same pathway, a double mutant was generated by crossing d14 with a known strigolactone-deficient mutant, d10. The resulting double mutant showed the same phenotype as d10 and d14 single mutants, indicating that d14 acts in the strigolactone pathway.

Further analysis revealed that d14 is insensitive to the application of strigolactone analogs, such as GR24, which inhibit the outgrowth of axillary buds in wild-type plants. In addition, the d14 mutant accumulates higher levels of endogenous strigolactones compared to wild-type plants.

To identify the gene responsible for the d14 phenotype, positional cloning was performed. The D14 gene was found to encode a protein belonging to the α/β-hydrolase superfamily. This superfamily includes proteins involved in signaling and metabolism of small molecules, such as plant hormones.

Discussion

The d14 mutant in rice provides valuable insights into the regulation of shoot branching and the role of strigolactones in this process. The D14 gene, which is involved in the strigolactone pathway, encodes a protein of the α/β-hydrolase superfamily. This suggests that D14 may play a role in the synthesis or perception of strigolactones.

The site of action of the branch-inhibiting hormone and the exact role of D14 in the strigolactone pathway are yet to be determined. Grafting experiments could provide valuable information about the localization of hormone synthesis or signaling. Further biochemical studies of D14 will also be necessary to elucidate its precise function.

The d14 mutant offers an opportunity to study the control of shoot branching in rice and its potential application in crop improvement. By understanding the molecular mechanisms underlying shoot branching, we can develop strategies to manipulate this process and enhance crop productivity.

Conclusion

The d14 mutant in rice exhibits enhanced tillering due to insensitivity to strigolactones. The D14 gene, encoding a protein of the α/β-hydrolase superfamily, is involved in the strigolactone pathway. Further research is needed to elucidate the precise role of D14 in the synthesis or perception of strigolactones and its implications for shoot branching in rice. Understanding the regulation of shoot branching in rice can contribute to the development of strategies for crop improvement.